Relatively recent innovations in building construction techniques and in the use of electrical non-metallic tubing systems (ENT systems) have increased the need for housings having features which facilitate mounting and provide increased bracing rigidity. Among the construction techniques are the use of metal studs, commonly steel, which are in the shape of a C having rather square corners when viewed in cross section. These studs are positioned vertically with the open side of the stud facing toward the next adjacent stud, leaving two side faces (the top and bottom of the C) available for the attachment of wall panels such as drywall or the like.
Housings for switches and outlets must then be attached to one or both of the other two faces, frequently the side which is mostly open. These studs have relatively short inwardly extending flanges into which fasteners can be driven, but each such flange provides a rather narrow support surface. It is therefore necessary to position the box carefully and to provide some other technique for bracing the housing in the installed location.
In addition, the metal studs are furnished in either one of two sizes, one size having a depth of 2.5 in. measured in the direction perpendicular to the wall panels to be attached thereto, and the other having a dimension of 3.625 in. in that same direction.